Abstract
N-acetylchitooIigosaccharides (fragments of chitin) elicit defense responses, including phytoalexin production, in suspension-cultured rice cells. They induced rapid and transient membrane depolarization accompanied by a transient increase in net CP−-efflux. The membrane depolarization was not affected by anaerobiosis or azide, suggesting that the major part of the depolarization was mediated by ion channels, not by energy-dependent ion pumps. Depolarization was partly inhibited in the presence of Ca2+- or Cl−-channel blockers and highly inhibited by depletion of Ca2+ in the extracellular medium. A calcium ionophore, A23187, caused a transient depolarization but not an increase in Cl− efflux, while it did not inhibit the elic-itor-induced transient depolarization and Cl− efflux. These suggest that the influx of Ca2+ from the extracellular space to the cytoplasm is necessary as an initial trigger but not sufficient for membrane depolarization, Cl− efflux, and the following signaling processes.
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